Getting Adequate Attic Insulation

By: Danny Lipford

No matter where you live in the U.S., homeowners are struggling more than ever before to find the balance between being comfortable inside their homes and keeping energy bills smaller than their mortgage payment.

Although adjusting your thermostat will help, the ultimate in energy savings is to keep the heat you’ve paid to produce within your walls as long as possible. That makes adding insulation one of the single most effective ways to save on heating costs.

In almost any climate, if you can see the tops of your attic floor joists when you venture up there, you’ll need to add more insulation. Depending on whether you live in a warm or cold climate, home in the U.S. should have between an R-38 and R-49 in the attic – that’s about 12″ to 15″ of insulation.

Go to the Dept. of Energy Zip Code R-Value Calculator to find insulation recommendations where you live. The DOE Website has a wealth of easy-to-access information about saving energy that is practical and accurate.

To determine if you need more insulation, use a ruler or tape measure to see how much insulation you have in your attic. When you do the measuring, make sure you have plenty of light to work because you will have to walk exclusively on the top edge of the joists—let your foot slip in between where the insulation is and you will end up breaking through the drywall or plaster ceiling in the room below.

Once you determine how much insulation you have and the amount you need, it’s easy enough to install additional amounts over existing insulation yourself. There are quite a number of insulation types including rigid foam, sprayed foam, mineral wool, and natural products like cottons and wools, but most attics in the U.S. are insulated with either fiberglass or cellulose.

Fiberglass

Fiberglass insulation comes in rolls or batts and is formed at a particular width and thickness to fit between studs in walls or joists in attics. Each thickness represents an R-rating standard (for instance, R-19 is 5½” thick for use with 2×6 wall studs or attic/floor joists).

Blown Fiberglass

This is fiberglass in a loose form that can be blown into your attic by a professional installer through a hose to whatever level is desired.

You can also rent blowers and buy loose fill insulation at home center to blow in insulation yourself.

Cellulose

Cellulose is a paper-based insulation (much of it recycled newsprint) treated with fire retardant that can also be blown into attics or walls with blower.

Which material you use is less important than making sure you have enough insulation for your climate. All of the insulation types above do a good job, and you do not need to stay with the type that’s in your attic now when adding more.

Here are some tips for installing insulation:

If you are installing fiberglass insulation in batt or roll form on top of existing attic insulation, make sure the insulation is unfaced and doesn’t have a paper or foil facing on either side.

Wear a long-sleeve shirt, long pants, gloves, eye protection, and a dust mask when installing insulation.

If you’re installing roll or batt insulation on top of existing attic insulation, lay it perpendicular to the joists so it doesn’t compress the existing insulation below it and creates a blanket with fewer areas where air can leak through from below.

Don’t cover can (recessed) lights unless they are rated for contact with insulation. If using loose (blown) insulation, build a small enclosure with hardware cloth or plywood to keep the insulation away from lights and exhaust fans.

Use cardboard or rigid-foam baffles to keep soffit vents from being blocked by insulation where the rafters rest on the outside walls. Encouraging this cold air circulation above the insulation will help exhaust moist warm air leaking from the living space below. If it can’t find a way out, it can condense and begin to rot the roof sheathing.

Fill all cracks between the living area and the attic with caulk or expanding foam. This includes areas where plumbing vent pipes, flues, electrical wiring, and vent fans, and light fixtures poke through into the attic. Sealing these voids helps defeat the “chimney effect” that draws cold air in at the base of the house and exhausts warm air (that you’ve already paid to heat) out into the attic floor.

If you are insulating walls or uninsulated joists, fill the cavity completely with insulation.

Don’t overly compress the insulation—it’s most effective in a fluffy state.

Split or cut insulation when you run into electrical wiring across the stud or joist bay.

In walls and floors, staple faced batts every 8″ to 12″ with the facing toward the inside of the house.

12 Comments on “Getting Adequate Attic Insulation”

I have an old house and it literally has no insulation. From the basement you can see all the way up the walls to the attic floor. Can I blow insulation down from the attic if I seal off joists in the basement?

I have papertype blown in insulation. There is no roof vents, only 2 soffits open and no baffle and don’t know if the 2 soffits have vent protection. There are very small vents on both corners of attic. I have been told there is not enough ventilation and could get mold and roof and beam rot.
The pulldown to access the attic is not protected. Can you help me as soon as possible so that I can contact the contractor and get the problem solved before it really gets cold up here in New York. I’m an elderly widow and I need your expert advise to do something now. Thank you for helping me. I enjoy watching you on the weather channel. Mrs. Marion Pringle

Why should attic insulation batts be unfaced? Is condensation the issue? How hard is it to get fiberglass unfaced ceiling batts?

The inspector for our home purchase said we could benefit by putting 4″ roll insulation on top of blown insulation in our ceiling, but I am assuming batts will work fine as the space is barely enough to use rolls.

That for the half of the house that has a ceiling space. The other half is a cathedral ceiling. Any ideas there? It was built in 1982.

Venting of attic or under roof space does NOT avoid condensation. When the roof gets down to dew point temperature, any humidity allowed thru ceiling insulation WILL condense on that cold surface. Soffit and ridge vents will NOT vent out humidity when surfaces are as cold as dew point!

Jamie, it’s easy to have additional cellulose blown over existing batts. In fact, you can often find the insulation and the blower at your home improvement store. Sometimes, if you purchase a specified amount of the insulation, they’ll let you use the blower at no charge. At eight months pregnant, though, just make sure someone else does the work! It’s as easy as point and shoot. Geez, I sound like a commercial for the Salad Shooter….

I love your show – just bought my first house and you are better than a handyman any day! I really want to get my attic insulated this summer…I am having a baby in a month or so. Can you please direct me to a good how to resource for installing additional cellulose insulation over existing bats in my attic. Most of what I find online is ilke reading another language!

Dan, I missed most of the info on the solar attic fan. Is it on your wab sight? Please advise! Jeff

We want to hear from you! In addition to posting comments on articles and videos, you can also send your comments and questions to us on our contact page or at (800) 946-4420. While we can't answer them all, we may use your question on our Today's Homeowner radio or TV show, or online at todayshomeowner.com.

Name (required)

Email (will not be published) (required)

Tips for Today's Homeowner

Sign up for Danny's Monthly Newsletter and stay up to date on tips and tricks for the home.